Hoist failed_uuids_path to single assignment in test()

Eliminates duplicated os.path.join computation in abort and normal
code paths, reducing divergence risk.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

toolchain/mfc/test/test.py

@@ -179,6 +179,8 @@ def test():
     cons.print("  Progress      Test Name                                        Time(s)   UUID")
     cons.print()
 
+    failed_uuids_path = os.path.join(common.MFC_TEST_DIR, "failed_uuids.txt")
+
     # Select the correct number of threads to use to launch test cases
     # We can't use ARG("jobs") when the --case-optimization option is set
     # because running a test case may cause it to rebuild, and thus
@@ -191,7 +193,6 @@ def test():
     # Check if we aborted due to high failure rate
     if abort_tests.is_set():
         # Clean up stale failed_uuids.txt so CI doesn't retry wrong tests
-        failed_uuids_path = os.path.join(common.MFC_TEST_DIR, "failed_uuids.txt")
         try:
             if os.path.exists(failed_uuids_path):
                 os.remove(failed_uuids_path)
@@ -223,7 +224,6 @@ def test():
     _print_test_summary(nPASS, nFAIL, nSKIP, minutes, seconds, failed_tests, skipped_cases)
 
     # Write failed UUIDs to file for CI retry logic
-    failed_uuids_path = os.path.join(common.MFC_TEST_DIR, "failed_uuids.txt")
     if failed_tests:
         with open(failed_uuids_path, "w") as f:
             for test_info in failed_tests: